The fact that there are so few difficulties during first solos suggest to me that the instructors have got it about right. I would however be worried if instructors started to compete with each other on average hours to first solo.
Good advice given to me prior to my first solo:
1. Remember it will go up a lot quicker without me in the aircraft (C152).
2. If you're not happy with the approach, throw it away and go-around. Don't try and land off a poor approach.
I did PFLs, and cross-country Navexs prior to my first solo which was at about 17 hours. I thought this was rather good until I read of the scores of pprune-ers who went solo in less than 10 hours.